In the field of driver circuits, there are many variations in solenoid driver circuitry used in industry today. The majority of these includes means for sensing the solenoid current to regulate the current in a closed loop system. In addition, most driver circuits use pulse-width modulation (PWM), or a variation thereof, to achieve a desired current delivered to a load.
In PWM driver circuits, the load is connected and disconnected from a power source according to a control signal. The control signal has a duty cycle proportional to the desired current. To vary the desired current, the duty cycle of the control signal is varied.
When the driver suddenly disconnects an inductive load from its power source, the current flow must continue. If no provisions are made, said current will produce destructive voltage spikes.
A majority of drivers place a flyback diode in parallel with the load. The flyback diode creates a path for the discharge of the flyback current. Generally, when the load is being energized, i.e., it is connected to the power source, the flyback diode is reverse biased by a positive voltage from the power source and no current flows through the diode. In other words, all current flows through the load. However, when the load is disconnected from the power source, the flyback diode provides a discharge current path to prevent the occurrence of large voltage spikes.
One disadvantage of this arrangement is that the diode may dissipate more power than desired during the flyback stage.
The present invention is directed to overcoming one or more of the problems, as set forth above.